3
air
atmosphere
blue
brick
brown
building
carbon
chemical
chemistry
chimney
chimneys
clear
climate
close
closeup
cloud
combustion
condensation
contamination
dioxide
dirty
emission
energy
environment
exhaust
factory
global
greenhouse
heat
industrial
industry
pipe
plant
pollution
sky
smog
smoke
smokestack
stack
steam
stone
three
tower
warming
white